Existing vehicle bumpers can be filled with foam. The foam provides impact absorption when there is an impact between the vehicle and an object, such as another vehicle. However, the foam does sufficiently reduce the force of the impact.
U.S. Pat. No. 6,148,970 discloses an energy absorbing system in which a piston travels within a fluid filled chamber, which has weak spots formed in a sequence along a length of the side wall of the chamber. When an impact force is applied to the piston, the movement of the piston increases the pressure of the fluid within the chamber, which causes the weakest of the weak spots to rupture. As the force is increased, the weak spots will rupture in sequence, providing a superior shock absorbing system.
In addition, U.S. Pat. No. 6,695,104 discloses a reusable energy absorbing system similar to that in U.S. Pat. No. 6,148,970. In this system, the impact force on the piston causes a discharge of fluid through two-way valves from the chamber into an elastic balloon structure. Then, when the impact force is removed from the piston, the fluid returns into the chamber from the two-way valve.
The present invention relies on principles similar to those in U.S. Pat. No. 6,148,970 and U.S. Pat. No. 6,695,104 in order to provide an improved impact energy absorbing crash cushion that is suitable for use as, for example, a vehicle bumper.